In the fields of civil engineering and construction, an emulsion of a synthetic polymer called an adhesion promoter is thinly coated on a concrete surface as a primer, or blended with cement mortar, etc., in order to improve workability, adhesion, physical strength, contraction, water absorptivity, etc., of cement paste, cement mortar, etc. As a proposal for improvement of adhesion of cement mortar, there is a process which comprises pre-applying a synthetic polymer emulsion to a surface in order to promote the adhesion of mortar, as is disclosed in Japanese Patent Publication No. B-Sho-44-18757.
Even if an emulsion of a synthetic polymer was used on a concrete surface or in cement mortar according to the above prior technique, the general performances of workability, adhesion, alkali resistance, weatherability, etc., are not sufficiently well-balanced. An ethylene-vinyl acetate-based emulsion has good hydrophilic nature and hence has good compatibility with cement and excellent workability. However, it has a defect that the polymer is susceptible to hydrolysis due to alkalinity of cement.
A styrene-butadiene-rubber-based latex has good alkali resistance. However, it has poor hydrophilic nature and hence has poor compatibility with cement. For this reason, its workability is inferior. Further, since it has a double bond derived from butadiene, its weatherability is poor.
On the other hand, an acrylic emulsion has high hydrophilicity, and therefore has good compatibility with cement. Further, it is excellent in alkali resistance and weatherability. However, its difficulty is that since none of its adhesion to a concrete surface, dry contraction and freeze and thaw stabilities are insufficient, the range of its application is naturally limited.